Multiple output waveguide switching systems



y 1953 J. s. HOLLIS 2,841,770

MULTIPLE OUTPUT WAVEGUIDE SWITCHING SYSTEMS Filed June 2, 1955 2 Sheets-Sheet 1 INVENTOR.

JOHN S. HOLLIS (ya/2M A TTOR/VE Y MULTIPLE OUTPUT WAVEGUIDE SWITCHING SYSTEMS JOHN S. HOLLIS ATTORNEY United States Patent MULTIPLE OUTPUT WAVEGUIDE SWITCHING SYSTEMS John S. Hollis, Charnblee, Ga., assignor to the United States of America as represented by the Secretary of the Army Application June 2, 1955, Serial No. 512,903

6 Claims. (Cl. 333 -7) This invention relates to rotary, multiple-output, waveguide switches for alternately connecting a single waveguide to a plurality of waveguides.

It is an object of my invention to provide an improved switch of this type in which the switching of a single waveguide to an even number of waveguides can be effected with a lower ratio of switching angle to operating (or scan) angle for a given operating bandwidth.

The type of switch to which this invention is particularly applicable is the so-called turnstile switch used in connection with rapidly scanned microwave antenna systems. In one system of this type, two pencil-shaped beams spaced in elevation about 2 degrees are scanned to azimuth over a sector of about 40 degrees. To provide for portability and a minimum amount of equipment, it is desirable to use a single wave-generator and antenna. For this purpose, the output of a single wavegenerator is alternately applied to two feed horns which 'irradiate a single reflector at slightly diiferent angles of elevation. Rapid azimuth scanning is accomplished by feeding the horns through two lenses of the modified Luneberg type having wide enough apertures to provide the 40 degree scan. Energy is alternately applied to the apertures of the lenses by alternately moving relative to the apertures a small feed horn at the end of a rotating waveguide which forms the output of a turnstile type of waveguide switch. For a further description of the Luneberg type of lens, reference is made to the paper of R. F. Rinehart, titled A family of designs for rapid scanning antennas, Proc. I. R. E., June 1952, pp. 686-688.

Since the scanning apertures of the lenses are about 40 degrees, a turnstile switch having eight output arms can be used to provide the most rapid scanning. However, the design of such a switch having that many arms presents numerous mechanical and electrical difiiculties.

A type of turnstile switch known in the art is illustrated on page 538, volume 9 of the Radiation Laboratory Series. A switch of this type comprises a central waveguide into which energy is introduced. A cylindrical barrier having a wave-transparent window is situated in this waveguide. A plurality of radially extending waveguide arms rotate relative to the barrier so that each arm successively passes the barrier window and receives energy therethrough, while the other arms are shorted by the barrier.

A more detailed design of such a switch is described in the paper of M. W. Long, titled A high speed K-band switch, in the Proceedings of the Institute of Radio Engineers, December 1951, pp. 1566-1567. A four-way turnstile switch of this type has been constructed in which the switching angle (or dead-time angle) is 20 degrees over a radio frequency band of :1 percent. For more than four outputs the ratio of the switching angle to the operating angle is too large, and the mechanical and electrical problems are greatly aggravated when more than six outputs are used.

, ice 1 The design of this type of switch represents a compromise between bandwidth and switching angle, which are both inverse functions of the barrier diameter. The bandwidth is also an inverse function of the number of arms. For small switching angles, a switch with a large number of output arms exhibits a prohibitively narrow bandwidth for most applications.

To overcome the above defect there is provided, in accordance with this invention, a pair of turnstile switches each having half the required number-of arms. The arms are mounted for rotation together and are so positioned relative to their lens apertures, that said apertures are alternately scanned. Energy is alternately supplied to these switches by a two-way rotary switch which during 180 degrees of its rotation supplies energy to one of the turnstile switches, while during the other 180 degrees of its rotation supplies energy to the other turnstile switch. The two-way switch is rotated in synchronism with the turnstile switches, but at a proportionately higher speed. The ratio of speed of rotation of the two-way switch relative to that of the turnstile switch is equal the number of arms of one of the turnstile switches. Thus in the case of two, four-arm turnstiles, the two-way switch will be driven at a speed which is four times that of the turnstile switches. This provides, for each output waveguide, an operating angle of about 42' degrees and a switching angle 'of about 3 degrees, which is one-fourth the switching angle of the two-way switch alone.

For a better understanding of the invention together with the other and further objects thereof, reference is had to the following specification taken in connection with the accompanying drawings, in which:

Fig. l is a schematic diagram of the invention;

Fig. 2 is an elevational view of one structural embodiment of the invention;

Fig. 3 is a plan view of another structural embodiment of the invention; and

Fig. 4 is a longitudinal sectional view taken along the line 4-4 of Fig. 3.

Referring now to Fig. 1, a source of radio-frequency wave energy in the microwave region (not shown) is coupled to a waveguide 10, which in turn is coupled to a two-way rotary waveguide switch 11. This switch directs energy through a waveguide 12 during 180 degrees of rotation, and through a waveguide 13 during substantially the next 180 degrees of rotation.

Waveguide 12 and 13 are respectively connected to rotatable waveguide switches 20 and 30, each of which has two or more outputs, four being shown in this case merely for purposes of illustration. Switches 20 and 30 are of the turnstile type, examples of which are described in the publications above cited.

Switch 20 comprises a rotor 21 into which extend four radially extending waveguide arms 22, 23, 24, and 25, spaced at intervals of degrees. Rotor 21 is a cylindrical cavity into which is applied the output of waveguide 12. Within this cavity is a cylindrical barrier 26 having an aperture or window 27 extending preferably about 90 degrees, although said angle can be as little as 45 degrees plus the angle subtended by one of the waveguides 22-25. As rotor 21 turns, waveguide arms 2225 successively pass by the window 27 and energy is transmitted through the window into each of the waveguides successively, the remaining waveguide arms being shorted by the barrier.

The free ends of the waveguide arms are preferably slightly flared as shown at 28 and form horn-shaped radiating apertures. As these arms move past the window 27, these flared ends move into registry with the arcuate aperture of a parallel plate waveguide 40 COIIl-j prising spaced, parallel plates 41 and 42. Aperture 40 extends over an angle of about 45 degrees and is angularly aligned with window 27 so that as a waveguide armmoves past the window, it scans the aperture of waveguide 40. The latter forms the input of the Luneberg type lens above referred to.

Switch 30' is. identical toswitch 20 and the elements 3 138 thereof function in the same manner as elements 21-48 respectively, of switch 20. The waveguide arms of switch3ti scan the aperture of a parallel plate-waveguide-50- which is the input to a second Luneberg type lens.

The rotors 21 and 31 are fastened together for simultaneous rotation by a motor 14; which is also coupled to the-rotor of switch 11' through-a reductiongear 15='-havingare'alternately scanned by the arms of switches and 30,

respectively, since just as one arm of switch20, say arm 23; reaches the end of its scanning path along the apertureof waveguide 40, an arm of switch 30, in this case arm 33, just begins its scan of the aperture of waveguide 50. Switch 11 is so phased that just as arm 33 begins its scan, energy will be switched from waveguide 10' to switch 30. Thus switches 20 and 30 alternately scan waveguides 40 and 50, respectively, every 45 degrees of" rotation thereof, and since switch 11 rotates 180 degrees for every 45- degrees of rotation of switch 11, energy is always channelled to the switch 20 or 30 which has a. waveguide arm in scanning position.

Although the system has been described from the point of. view of scanningtransmitted energy, it functions-also in reverse manner for receiving purposes.

Output arms 2225 and 32-35 in this case are mounted on a rotor because in this case theyalso perform a scanning function. But where no scanning is required and merely a switching function is to be performed, both the inputand output arms can be made stationary and barriers 26 and 36 rotated.

The maximum number of arms on each turnstile. switch is dictated by the .size of the sector to be scanned. Four. arms are used in this case because the aperture of'waveguide 40 which is alternately scanned by'the arms is about 40 degrees in extent. If a 90 degree sector were to be. scanned, then each switch would have two arms, each of the barrier windows 27 and 37 would extend over an arc of 180 degrees, and switch 11 would be rotated'at.

only twice the speed of switches 20 and 30.

In general, if switch 11 has a plurality of M switching actions per revolution, and switches 20 and 30Ieach have a plurality of N switching actions per revolution, then the gear ratio R should'be such that M equals 2N. Thus, in the case above described, both MR and 2N equal 8. From another point ofview the relative rotational speed shouldbe such that ina given time the number of switching actions of switch 11 must vbe equal tothe combined number of switching actions of switches. 20 and 30. Thus, during one rotation of switches 20 and 30, eight switching actions are made by said switches. During this. time, switch 11 makes four revolutions andtherefore eight switching actions.

The above described system can be further extended in several ways. Thus if switch 11 has four evenly spaced outputs, the said outputs can be applied to fourzmultiposition switches, such as 20 and 30, all-rotated at the same rate. As in the present case, the outputwaveguidesof the four switches'would be staggered relative to each other, so each makes a switching action. insequence.

Another method of extending this principle is. to provide two or more complete systems such as shown in Fig. l, with theinput waveguide 10of each system being fed from an additional switch having two outputs which are alternately excited. This additional switch would have to be geared for rotation at twice the speed of switch 11, assuming that it has two outputs. This method of pyramiding switching circuits can beapplied to systems for supplying any number even of outputs from a single input. In addition it is not limited to waveguide switching, and may be used for switching ordinary conductive circuits excited with either direct or alternating current.

The advantages of the system above described will be better understood if a single turnstile switch is considered. The operatingv angle of any one arm of the switch is smaller than the width of the barrier window, since the arm does not transmit power effectively until the full width of the waveguide arm in the direction of rotation comes into registry with the window. The angle of .rotationnecessary to bring'the arm into full registry is known as the switching angle or dead-angle, and the time it takes to come into registry is known as the switching time or dead-time, the latter being inversely proportional to thebarrier radius. Unless the width of the waveguidearrn is very small, with consequent restriction of thefrequency band, or the radius of the barrier is very large compared to the width of the waveguide, the switching angle is appreciable compared to the operating angle; and because of this a single turnstile switch having more than six arms is not feasible.

With the dual four-switch system as above described; eachfour-way switch 20 or 30 has a 45 degree switching angle while the other switch is active and the switching angle is one'fourth that of the two-way switch. This.

switch can be of the chopper type, such as described on pp. 533 and 534 of vol. 9 of the Radiation-Laboratory" Series, entitled Microwave Transmission Circuits,. by Ragan; Since, such switches can be constructed with switching angles as low as about four degrees, the effec tive switching angle of the entire system above described can be as. low as'one degree. In general, the switching angle of the system will be that of the switching angle of thetwo-way switch divided by the ratio between the speeds of rotation of two-way switch and the output switches. The-limit of; allowable switching angle of the output switches is" 360 degrees divided by the total number of output arms of both switches, plus the system switching angle.

Reference is now made to Fig. 2, which shows a.struc-. turalembodiment of .the system in Fig. 1. To avoid repetitionin description, the elements in Fig. 2 which corresponds-in function to those of Fig. 1 have been given the same'reference numeral with a prime mark added. Thus element in Fig. 2.corresponds to element 10 in Fig. 1, etc; Switches 20 and 30 are mounted one above the other, and switch arms 22', 23', etc., and 33', 34",,etc., are mounted on a single rotor 60, which is driven by motor14through bevel gears 61 and 62. Gear 62 is also. coupled, through gears 63, 64, and 65 to the rotating shaft of switch 11, the gears being proportioned to drive switch 11 four times as fast as rotor 60.

Figs. 3 and 4'illustrate anotherstructural embodiment of the system in Fig. 1. Here too, an element which corresponds in function to a given element in Fig. 1 is given the same reference numeral with a double prime markadded. Here, the turnstile switches are of the ring type. described and claimed in the copending applicationof-JohnS. Hollis, and Maurice W. Long, S. N. 507,516, filed May 10, 1955, entitled A Low-Loss Waveguide Ring; Switc Switch 20" comprises a torus-shaped waveguide 70 which is aixally split at 71 to-forman innersection 72 and a complementary outer section 73, concentrically arranged. The lower switch 30." is similarly constructed. The outer sections of the ring switches are respectively supported upon the top and bottom'of. a rotating support 74, while the inner sections of said ring switches are supported upon the top and bottom of a stationary support report 75. The adjacent faces of said supports form a raceway 76 for ball bearings. Two-way switch 11" is mounted coaxially with the ring switches. Input waveguides 12" and 13 communicate with the inner sections of rings 2% and 30", respectively. Output waveguides 22-25 extend from the outer section 71 of ring switch 20 while output waveguides 32" -35 extend from the outer section of ring switch 30". Because of the coaxial arrangement of the various switches, a more compact and efiicient structure is made possible in certain cases. The means for rotating said switches is not shown.

While I have described several embodiments of the 1nvention, numerous changes may be made without departing from the invention, and it is aimed in the appended claims to cover all such changes which fall within the scope of the invention.

l. A waveguide transmission system comprising first, second and third waveguides, a first rotary waveguide switch connected to said waveguides to alternately couple said first waveguide to said second and third waveguides, second and third rotary waveguide switches having an equal plurality of branch waveguides, each of said second and third switches comprising a central waveguide having a wave-transparent window in its surface, said branch waveguides having open ends symmetrically arranged about said central waveguide, whereby upon relative rotation of said central and branch waveguides said open ends sequentially register with said window, the circumferential length of said window being greater than that of each of said open ends, but smaller than the circumferential spacing thereof, means coupling the rotatable elements of said second and third switches for rotation together at the same rate, the elements of said second and third switches being arranged so that the registry of the window and an open end of a branch waveguide of said second switch alternates with the registry of the window and an open end of a branch waveguide of the third switch, means to couple said second and third waveguides to the central waveguides of said second and third switches, respectively, and means coupled to said second and third switches for simultaneously rotating said first switch at a higher speed than said second and third switches, the ratio of the speed of said first switch relative to the speed of said second and third switches being equal to the number of said branch waveguides on each of the latter switches.

2. A waveguide transmission system comprising first, second and third waveguides, a two-way rotary waveguide switch connected to said waveguides to alternately couple said first waveguide to said second and third waveguides during successive 180 degree rotations of said switch, second and third rotary waveguide switches having an equal plurality of branch waveguides, each of said second and third switches comprising a central waveguide having a wave-transparent Window in its surface, said branch waveguides having open ends symmetrically arranged about said central waveguide, whereby upon relative rotation of said central and branch waveguides said open ends sequentially register with said window, the circumferential length of said window being greater than the circumferential spacing of said open ends, but not greater than 360 degrees divided by number of branch waveguides on one of said second and third waveguide switches, means coupling the rotatable elements of said second and third switches for rotation together at the same rate, the elements of said second and third switches being arranged so that the registry of the window and an open end of a branch waveguide of said second switch alterntaes with the registry of the window and an open end of a branch waveguide of the third switch, means to couple said second and third waveguides to the central waveguides of said second and third switches, and gear means coupled to said. switches for simultaneously rotating said two-way switch at a higher speed than said second and third switches, the ratio of the speed of rotation of said two-way switch relative to that of said second and third switches being equal to the number of said branch waveguides on each of the latter switches.

3. A waveguide transmission system comprising first, second and third waveguides, a two-way rotary waveguide switch coupled to said waveguides to alternately couple said first waveguide to said second and third waveguides during successive 18 degree rotations thereof, a pair of turnstile switches each comprising a central waveguide having a wavetransparent window in its surface,

'said turnstile switches having an equal plurality of uniformly spaced branch waveguides having open ends symmetrically arranged about the central waveguides thereof, whereby upon relative rotation of said central and branch waveguides said ends sequentially register with said window, the angle subtended by said window being equal to 360 degrees divided by the number branch waveguides on one of said turnstile switches, means coupling the branch twaveguides of both turnstile switches for rotation together at the same rate, the elements of said turnstile switches being arranged so that the registry of the window and an open end of the branch waveguides of one of said turnstile switches alternates with the registry of the window and an open end of the branch waveguide-s of the other, means to couple said second and third guides to the central waveguides of said turnstile switches, respectively, and means coupled to said turnstile switches for simultaneously rotating said two-way switch at a higher speed than that of said turnstile switches, the ratio of the speed of rotation of said first switch relative to the speed of said turnstile switches being equal to the number of branch waveguides on each turnstile switch.

4. An energy distribution system for sequentially connecting a circuit to a plurality of other circuits comprising a first rotary switch having its input connected to said first-named circuit and having a plurality of selectable, symmetrically-spaced outputs, an equal plurality of additional rotary switches having their inputs respectively connected to each of said outputs, each of said additional switches having a plurality of symmetricallyspaced selectable outputs, said additional switches being tied together for simultaneous rotation and so phased relative to each other that the energization of the outputs of each is interspersed with the energization of the outputs of the others, and means gearing said first switch to the other switches for rotation at a higher speed than said other switches, the speed ratio being such that the number of switching actions of said first switch in a given time interval is equal to the combined number of switching actions of all of said additional switches during the same time interval.

5. An energy distribution system for sequentially connecting a circuit to a plurality of other circuits comprising a first rotary switch connected to said first-named circuit and having a plurality of M selectable, symmetrically-spaced, circuit-making positions, M additional rotary switches respectively connected to each of said positions, each of said additional switches having a plurality of N selectable, symmetrically-spaced, circuitmaking positions, said additional switches being tied together for simultaneous rotation and so phased relative to each other that the circuit-making positions of each is interspersed with the circuit making positions of the others, and means gearing said first switch to the other switches for rotation at a higher speed than said other switches, the speed ratio being such that during each revolution of said additional switches, said first rotary switch makes N revolutions.

6. An energy distribution system for sequentially connecting a circuit to a plurality of other circuits comprising a first switch connected to said first-named circuit and having a plurality of selectable, circuit-making positions, a plurality additional switches equal in number to the. number of said positions and respectively connected to said positions, each of: said-additional switches having a. plurality circuit making positions, said additionalswitch'esbeing: tied together for simultaneous operation;

and so phased relative to each other that the circuitmakingrpositions of each is interspersed with the circuitmaking positions of the others, and means gearing'said first switch to the other switches for operation at a higher speed, the speed ratio being such that the number of switching actions of said first switch in a given time interval isequal to the combined number of switching actions 8 of all of said additional switches during the same time interval.

References Cited in the file of this patent UNITED STATES PATENTS 

